The orthostatic changes in heart rate (HR) and blood pressure (BP) were recorded in ten patients with stable angina pectoris before and after simultaneous sublingual nitroglycerin administration. All patients were examined three times: without other medication, during chronic metoprolol treatment, and during chronic verapamil treatment. Under control conditions, only minor changes were found in systolic BP following vertical tilting, while diastolic BP increased by approximately 10%. Nitroglycerin augmented these changes to some extent, while neither metoprolol nor verapamil caused significant changes. The orthostatic HR increase was considerably augmented by nitroglycerin. Verapamil treatment did not influence this response, while metoprolol caused significant reductions. These findings seem to explain why some few patients have observed severe orthostatic symptoms while taking nitroglycerin during treatment with beta-adrenergic blocking agents.